EP2040893B1 discloses a shaver having a light source which projects an image, such as a line segment onto a user's skin during use of the shaver. The line segment is configured to indicate the position of the edge of the razor blade to allow the user to judge the extent of the shaving action and position the shaver appropriately. The shaver has a light source which projects a line segment either directly onto the skin or onto a reflective surface which reflects the line towards the skin of the user.
With devices such as those known from EP204893B1, the line segment may suffer from poor definition and focus as it is difficult to collimate the light beam into a concentrated line projection that extends for any significant length.
Typically, when an optical line is generated, parts of the line furthest from the light source will have a lower intensity and therefore a lower visibility than parts of the line closest to the light source. Therefore, the parts of the line furthest from the light source will be less visible to a user.
Furthermore, when projecting an optical line against skin, for example for use with a shaver, the intensity of the light emitted is subject to safety regulations. Light may interact with the skin or the eyes and cause irritation or damage. Regulations stipulate a limited light intensity to ensure that these risks are minimal. However, because the line will have variable intensity along its length, as previously explained, the power of the light source has to be increased to achieve sufficient visibility in the parts of the line furthest from the light source. However, this also increases the intensity of the light in the other parts of the optical line, which may cause problems in the parts of the line closest to the light source. It is also important to ensure that the intensity of the light is not so high that it could cause irritation or injury in the event that it is inadvertently deflected away from its desired optical path which may occur, for example, if the shaver is damaged.